NTSB/AAR-70/28 - AirDisaster.Com

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TMAS INTERNATIONAL AIRTJNES, INC.
DOUGLAS E-9, Nl308T
HARKCNGR?, TMAS
JANUARY ll, 190
TAELE OF CONTENTS
Synopsis...............
Probable Cause . . . . . . . . . . . .
Investigation . . . . . . . . . . . . .
* - - *
Injuries to Persons . . . . . . . . . . .
History of Flight . . . 0
Damage to Aircraft . . . . . . . . . . . . .
OtherDamage. . . . . . . . . . .
migatmew rnfarmation . . . . . . . . . .
Aircraft Information . . . . . . . . . . .
Meteorological Information . . . . . . . . .
Aids to Navigation . . . . . . . . . . . .
Communications . . . . . .
Aerodrome and Ground Facilities .
.
.
.
. . .
Flight Recorders . . . . . . . . . . . .
Aircraft Wreckage . . . . . . . . . . .' .
Fire . . . . . . . . . . . . . . . .
SurvivalAspects . . . . . . . . . . . .
Tests and Research . .I . . . . . . . . . .
Analysis and Conclusions . . . . . . . . . .
Analysis . . . . . . . . . . . ... . 0
Conclusions . . . . . . . . . . . . . .
(a) Findings . . . . . . . . . . . . .
(b) Probable Cause . . . . . . . . . .
Recammendations and Corrective Measures . . . . .
Appendices
A. Investigation and Hearing
1. Investigation
2. Hearing
3. Preliminary Report
B. Harlingen Approach Chart
C. Flight Recorder Dsta Graph
D. Letter to Honorable JON H. Shaffer, Administrator,
Federal Aviation Administration, dated November 20,
1970

SI3 71-7
(202) 426-8787
Office or the klyirman
The Sational Transportation Safety lloard released tday its
report on a predawn approach accident in which a Texas Inter-
national Airlines Ilouglas Dc-9 nearly crashed on approach to
Ilarlingen. 'Texas. on January 11. 1!'70.
The aircraft struck a 30-to-35-foot-hiph tree and two ?!'-foot
power poles more than two miles short of Ilarlingen Industrial
Airport. The crew &as able to abort rhe approach, climb awag,
and continue safely to a landing at Houston even though the sub-
.stantially damaged Dc-9 was carrying pieces of tree. pole and
wire Imbedded in its underside. Ilarlingen visibility at the time
of the approach, 0700. was reported as one-half mile in fog.
All il persons aboard the aircraft escaped injury.'
The Safety Board determined that the probable cause was . .
,*
. . . the continuation of the descent, during actual
instrument conditions, through the Ninimum Descent
Altitude and into ground obstructions as a result of
inadequate flightcrew monitoring of the aircraft
altimeters. A contributing factor was a lack of
awareness by the flightcrew of the actual meteorological
conditions, caused by crew fatigue. and
company workload p r i o r i t i e s w e d
normal air-to-ground communications and deferred
the dissemination of essential meteorological
.I
information.
The Safety Board's investigatiqn showed that the captain and
first officer had logged 4335 hours of flight time the day before
.

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the accident. 'I'ltcy Itad remained overnifltt at .UcAllen -- departuro
point for SLc.\llen-lIarlin~tn-Ilon~ton-lhllas FliEht 926. Rut they
could have lad only about fowr hours' sleep before the accident
flight, the Board found. The plots had arrived at the Mc..\llen
airport at the 0630 scheduled departure time for Flight 926. and
in about 2t minutes performed their pre-flight duties. taxiied out
and took off. The Ihard held that hth the rest period and the
flight preparation had been "inatlcquate. .,
The llarlingen weather report receired by the captain before
the takeoff from McAllen was an 0500 report of clear skies and
visibility of five miles. An 0600 repnrt of one-mile visibility at
Harlinqen was not made to IlcAllen because .. of "the heavy workload
at the company's Ilarlingen station. the Hoard said. Thus
noth the captain and the first officer, who was flying the 25-mile
Xlc.~llen-llarlingen segment, were "not aware of the actual weather
conditions at ilarlingen" when they began their approach, the Board
found.
'hring the descent, the first officer was primarily occupied
with establishing and maintaining proper heading and -- believing
visibility to be about five miles -- .. locrkiaq out of the cockpit
.I
for airport lights, the Board said. "The variance of altitude
I.
during this period, as shown by flight dam recorder evidence,
,a. ..
Indicates inadequate monitoring and control.
The captain. who during cruise had been unable tn contact
his company's llarlinaen station, did mahc radio contact during
the approach. l'olrl chat Ilarlingcn at 0655 had half-mile visibility
in fog, the captain replied that the last weather the crew had
received was clear skies and five miles, and Flight 326 was then
on final approach. It was at abou: this poinr. the Board determined.
that the captain ordered the first officer to level off. The Board
said it believes the order was given by the captain "as a result
of his receipt of the new weather information. " Impact with the
tree and poles came a fer seconds later.
The Board's invest,igation developed w failure or malfunction
of the aircraft. its powerplants or systems. Flight data recorder
evidence showed that the aircraft had been within 130 feet of known.
assigned or published altitudes from takeoff at McAllen to landing
at Houston. Investigation and testing of ho possible sources of
out-of-tolerance leakap in the aircraft static pressure systems
led to a Boprd conclusion that neither would have had "appreciable
effect" on the cockpit altimeter readings.
Findiog that some altimeters in Tam International aircraft
bore low-altitude warning markings but others did not, the Sofety
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..
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Board on Sovember 20, 1970. recommended that the Federal
Aviation Administration consider requiring standardization of
such markings on all instrcments in an air carrier or air taxi
operator's fleet. FAA agreed that pilots should be able to expect
I,
standardization of critical flight instrument presentations." and
said it was "carefully considering" how this could be achieved.
The Hoard also noted that FA4 had raised Tesas International's
landing minimums aher the accident, and that the carrier had
taken steps "to improve and increase pilot proficiency. ..
. .
. .
6 -

Adopted: Decuber 2, 190
NATIOXAL TRANSPORTATION SAFZTY L?QARD
WASW!CMN. D. C. 20591
File no. 1-ooCe
7

1.1 Histpry of Fliqht
. .. ~
Texas Tnternationnl Airlines (TXI)' Fllqht 96 is a re&.arly I L
schedded doaestic pessenjer/ear%o flight which operates betseen
McAllen. Texas (m), and ikllas, Teras. with ochednled en rode stops I
at Harlilyen (m) and bustan, Texm (IAH). "he flig3t originates at f
Mc4llen and the aircraft and cmw are the a ~ tbat ~ e teininate %n KcAllen
in the late afternoon of the previous day and remain overnight. Sched- m i
uled departure of TXI 96 is 0630. 1
Cn January 11, 1970, the fl#&creu of MI Flight 96 nrrived at .' '- i
the NWen Airport about 0630. The captain stated tbst upm llis arrival i
'at the airport, he ". . . vent, to Opemtions, sigled w release, ckecked
i
tie weather and got eU the wailable %:ht Pclpus." The flrst officer ~ i
@/O) checked the airplane. "he fliatcrev .then 5et in the cockpit, ran i
i*
b hecklists, and started engires. In a stntenent dated Jan- 13, lg0,
i
e captnin stated, '%e received our cleaiance f'rrm .W at the ranp wMch
' c leared to V-2S mintsin 2(?00 feet,' set our altimeters, accau-
.plished oar check lists, etc. Departure was normal rrith the F/O at the
controls for this seaent." me flight. took off at E.FE ebout C65l.
did~not :have M ultlaeta setting fmm t:?e Ccmpany and I dcn't believe
-r
f

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"Mments later we incurred a bump, a thud, as if a bird had hit
that's what it sounded like or felt like to us, it wasn't a real
one. Then I said, 'lets get out of here, missed approach, they
en't got it'. We executed a missed approach to the left, ran our
cklist, climbed to our missed approach altitude and proceeded to the
. I advised Brownsville approach, we had made a missed approach and
quested clearance to Houston."
The first officer stated: 'we ran the Before Takeoff as per
cedure and we were ready to go. McAllen cleared us for takeoff for
right turn out on course. We climbed out, I was flying and after
an-the After Takeoff we turned on course. I seem to recall some
8 sticking up north of tarn, but I can't say for sure because it was
. I made a right turn intercepted victor 20 south and proceeded on
tain Capps called McAllen and reported level at 2000. Later
called BRO and got a clearance for an approach to RRL. We
approach and descent checklist and we started letting down to
e for crossing the VOR (1600). After crossing the VOR, we
et dam to OUT minimum approach altitude which without the
'8 altimeter setting, I believe, is 635. With Bramsville's
eading, its minimum is 680. The checklist had been m,
ch and descent and everything was looking real fine.
"As I was making the approach, the Captain started calling out our
o me at about 500 feet above minimums and he proceeded to do
h 100'. As I approached within probably 100' minimum altitude,
tain'told me, "Gib, hold it there'. So I leveled off and
after this, we had a bump. It was nothing more than a - I'd
se bumps on the road, I know that. The Captain then told me, let's
of here. I pushed the throttles forward, pitched up to 15 and
a missed approach."
., BRO Apc cleared Flight 926 to Houston Intercoptinental Airport (M)
an altitude of 23,000 feet. As the flight was approaching 12,000
in the climb to 23,000 feet, the cabin pressurization warning light
on. The crew requested U,OOO feet cruise altitude, which was
ved, and proceeded to Houston at that altitude.
o passengers, sitting on the left side of the aircraft, called a
ess' attention to a "gash" in the leading edge of the left wing.
stewardess advised the captain of this condition. Shortly afterward,
first officer came to the cabin, visually inspected the wing, and
returned to the cockpit to continue the flight to Houston. A paser
later stated that the man who came back to look at the hole got
of the right seat.
eather minimums for landing.
sville Approach Control was unable to obtain the latest Harlingen ~
er.. Flight 926 did not request the Brownsville altimeter seB3ing
none was provided.
amaville Approach Control.
i
'!

~ left
-rr 1.3
When the flightcrew lowered the landing gear during the approach
to land at Houston, the hydraulic system low pressure warning lights
came on and an unsafe condition was indicated for the nose gear and
main landing gear. The crew extended the landing gear using the
manual extension procedure and a safe-to-land gear indication was
obtained for all landing gears, About 0810 the aircraft landed safely
at Houston.
After the aircraft rolled clear of the landing runway, the crew
stopped on the taxiway and maintained engine power on until ground per-
sonnel could install safety pins in the landing gem linkage. When the
landing gear safety pins were in plsce the engines were shut down and
the aircraft was tawed to the terminal where the passengers and the crew
deplaned in a n o d manner.
1.2 Injuries to Persons
There were no injuries to the four crewmembers or to the 37 paslksengers
on board.
Damage to Aircraft
Several pieces of tree limbs and pieces of telephone poles were
found embedded in the tears and holes. A piece of copper wire, with an
insulator attached, was embedded in the leading edge of the left wing
and trailed over the top and bottom of the wing.
1.4 Other Wage
Other damage occurred in proximity to the home of a ground witness.
This home is located about 12,000 feet short of the threshold of Runway
13 at Harlingen Industrial Airport, approximately on the 108" radial of
the HRL VOR. A hackberry tree about 30 to 35 feet tall, in the back-
yard of the home, was destroyed. Two power poles 29 feet high, located
in front of the home, had about 4 to 6 feet of their tops broken off,
which necessitated the replacement of both poles and several hundred
feet of utility wires. A jeep parked at the residence sustained a
shattered windshield.
Captain Jerry Eugene Capps, aged 40, holds ATR Certificate No.
1243323, AMEC, with ratings in Convair 240, 340, 440, E-3, cv-600,
and X-9 aircraft. He also holds commercial privileges for &Et. Ills
total flight time was 15,715 hours, with total time in the E-9 of 818
Harlingen very high frequency omnidirectiod radio range.

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hours. His last line check and proficiency flight check were passed
satisfactorily on April 14, 1969, and December 3, 1969, respectively.
ms last first-class medical examination was passed satisfactorily on
July 25, 1969, with no limitations or waivers noted.
First Officer Gerald Forest Gibbons, aged 35, holds Commercial
Pilot Certificate No. 1370654 with airplane single-and multiengine land
and Instrument rating. His total flight time was 7,363 hours, with
total time in the W-9 of 454 hours. His last line check and proficiency
flight check were passed satisfactorily on October 2, 1969, and IYovember
4, 1969, respectively. €Es last first-class medical examination was
passed satisfactorily on September 15, 1969, with no limitations or
waivers noted.
Crew Activities
4,o~&&35 :ianaaxb,w3the
~di3Sn about .LT@ on
:as the erar-of !UI FUght 967 which tenuinated at McAllen.,
The TXI Harlingen Station Manager and his wife, the captain, the first
officer, both stewardesses, and the parents of one of the stewardesses
spent the evening of January 10 in Mexico where they.dined together.
Both stewardesses and the one stewardess' parents returned to
McAllen about 2230. According to the TXI Aarlingen Station MaimP"g
he and his wife
m.., ,. . 888 based aWI4?4kUm 8W the oaphin and the fipt Officw
ar -:*-om+#, &el between and
arin the8 at that time.
The first officer stated in part: "We all reported darn to the
motel office to leave for the airport . . . This was probably at
6:OO or right close to it, and the Captain hadn't returned yet. The
hotel took us to the airport."
An extensive investigation into the flightcrew's activities on
the night of January 10 accounted for all their activities and whereabouts
except during the period between midnight and about 0415 on
January ll, 1970.
A "XI Convair 600 flightcrew.

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1.6 Aircraft Information
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Douglas E-9-31, Iil308T, is awned by General Electric Credit
Corporation and operated by Texas International Airlines, Inc. The
aircraft manufacture date is December 15, 1968. The aircraft had
accumulated a total flying time of 2,281 hours. The last major
maintenance inspection was accomplished on December 30, 1969. This.
inspection included a test of the pitot static system. The inspection
was satisfactory, with no discrepancies noted.
The aircraft maintenance inspection records and the aircraft logbook
pages for December 1969 and January 1970 were reviewed. Particular
emphasis was placed on repeat/trend type items and discrepancies covering
the pitot/static/alltimeter systems. This review disclosed no qpen
or uncorrected discrepancies, no "trend" type items, and no prior mal-
Punctions of the aforementioned systems or their components.
Meteorological Information
11.7
' There is no Weather Bureau station at Harlingen, Texas. Harlingen
weather observations are made by Texas International Airlines personnel
and sent via teletype to other stations. These observations are made at
5 minutes prior to the hour and transmitted on the hour. The following
observations were made at Harlingen on January 11, 1970:
0455 clear, 5 miles visibility with fog
0555 clear, 1 mile visibility with fog
0655 partial obscuration with 112 mile visibility in fog,
temperature 48"F., dew point 47"F., wind 310" at
6 knots, altimeter setting 29.91.
(The 0455 observation was with the flight papers for TXI Flight
926. The 0555 observation was not.)
Mr. Elder Black, a TXI employee at Harlingen, stated in part:
"The six o'clock weather was taken by Joe Reyns, but was not sent due
to being rushed by telephones, ticket counter, and trying to get pas-
sengers checked in."
Mr. Joe Reyna, a TXI employee at Rarlingen, stated in part: "I
came on duty at 6:OO am, checked the weather with Mr. Black, we both
agreed that we had about one mile visibility, with the sky and stars
visible. Mr. Black had already sent the weather report . . . " Mr. Reyna
f'urther stated: "The Mwen agent, Mr. Johnny Vasquez, advised me
that flight 926 was trying to contact us on the company radio, I then
went to the operations room to monite (sic) the radio. I called for
flight 926, and they answered immediately, flight 926 asked what our
late weather was so I gave them the 0655 observation, which I had just
taken. I advised 926 that Harlingen had -X skies and about 1/2 mile
visibility with fog. I gave the wind direction as 30 degrees at six
knots. Flight 926 then replied that the last weather they had was clear
Partial obscuration - sky more than 1/10 but less than 10/10 obscura-
tion.

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skies and five mile visibility and that he was on final . . . about
five minutes later I heard the flight going over. "
The weather at MFE (35 miles west of HKL) at the time TXI 926
departed was: sky partially obscured, visibility 1/4 mile in fog.
TXI 638 departed MFE about 1 minute prior to TXI 926 and reported
the top of the fog was 700 feet m. s .l. and clear above. The
captain of TXI 638 made an IFR approach to Harlingen Industrial Airpark
(which was missed) a few minutes after TXI 926 made its approach. He
stated: "The cloud tops were 450' MSL on altimeter."
The ground witness whose tree was struck by Flight 926 stated
that after the impact he went outside and "it was so fo0g.g I couldn't
see more than 50 yards." He also stated that it was dark and he had
his house lights on until the aircraft struck the parer poles and the
lights went out. He said that both of the electric clocks in his house
had stopped at 7 o'clock.
The altimeter setting at McAllen was 30.01 at 1700 on January 10,
1970, the approximate time that the crew landed to terminate Flight
967. 2/
1.8 Aids to Navigation
The Harlingen (HRL) VOR is located 8.1 miles from the threshold
of Runway 13 at Harlingen Industrial Airpark. The inbound radial from
the WR to Rurrway 13 is 108". The accident occurred approximately on
this radial.
The Jeppesen Approach Chart available to the crew for the VOR
approach to Runway 13 at Harlingen (see Appendix B) shows the airport
elevation is 35 feet. The VOR crossing altitude inbound is 1,600 feet
m.s.l., and the minimum descent m.s.1. altitude and minimp-visibility
for a E-9 aircraft making a circle-to-land approach ar8600 - feet,ynd
1 1/2 mile$, respectively, using the Harlingen altimeter setting or
68O~~feet and 1 1/2 miles, respectively, when the Brarnsville altimeter
setting is used.
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On January 11, 1970, the Bramsville CS/T reported that the
HliL VOR was operating normally.
1.9 Communications
There were no reported technical difficulties with communications.
The crew did encounter Borne operational difficulty when trying to contact
the TXI Company radio at Harlingen where all of the TXI personnel were
busy in connection with the anticipated arrival of TXI Flights 926 and
638.
lOJ Mean sea level.
The same aircraft and crew were used for Flight 926 of January ll.
l2J Br-ville Combined Station and Tower Facility.

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1.10 Aerodrome and Ground Facilities
Harlingen Industrial Airpark has no control tower. IFR traffic
into and out of FIarlingen is controlled by Bramsville Approach Control.
1.U Flight Recorders
KL308T, Flight 96, was equipped with a Fairchild Model AlOO cockpit
voice recorder (m), S/N 1388. This recorder was removed and sent to the
National Transportation Safety Board, Washington, D. C., for examination
and evaluation of the tape, The CVR contains approximately a 30-minute
supply of tape in a continuous loop. When electrical power is applied
to the CVR, the tape is erased immediately prior to passing over the
recording heads. Therefore, only the last 30 minutes of conversation
and sounds, prior to power interruption, are recorded on the tape. The
aircraft was flam for over an hour after the accident occurred. Electrical
power was continued on the aircraft after the landing at Houston,
$nd subsequently electrical power was applied to the aircraft by ground ,
phrsonnel while the CVR circuit was energized and the recorder was still
installed; therefore, no useful information could be obtained i2.om the
voice recorder tape.
Nl308T was equipped with a Fairchild flight data recorder (FDR),
5424-502, SIN 5034. The magazine from this recorder was removed and
sent to the National Transportation Safety Board, Washington, D. C., for
examination and a tape readout of that portion of the flight record per-
tinent to this accident. The findings of the readout, based on the
latest available calibration data, disclosed that the altitude and air-
speed parameters were out of calibration on the high side by a significant
amount (see Section 1.15 Tests and Research). A data graph was prepared
from the readout of the accident flight record (see Appendix C).
1.12 Aircraft Wreckage
Not involved. Small miscellaneous pieces of the aircrafi - mostly
wing and fuselage skin - were found at the accident site.
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1.13 Fire
Not involved.
1.14 Survival Aspects
Not involved.
1.15 Tests and Research
Altimeter/Static System Tests

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systems by removing the caps from the drain port lines within the nose
gear wheel well (unpressurized area) and fastening the test set to the
ports in turn. The static ports were taped over. Leaks in excess of
275 feet per minute (f.p.m. ) in both systems were encountered. Maximum
allowable leakage is 175 f.p.m. TXI mechanics stated that they had
previously had difficulty with certain aircraft in securing an airtight
connection between this test set fixture and the static drain ports.
The test set was removed and the drain ports recapped. The captain's
and first officer's altimeters were removed from the aircraft and the
test set connected to the lines normally fastened to the two altimeters.
At this point, one of the mechanics assisting found that the "B" nut
employed to fasten the captain's static line to the starboard static
port in the forward cargo compartment (pressurized area) was not
properly torqued. The "B" nut was tightened 3/4 of a turn which
properly torqued it, Notwithstanding this correction, both systems
still had out-of-tolerance leaks. It was determlned that the source
of leakage was at the static drain port caps in the nose gear wheel
well area.
The test equipnent was removed from the altimeter connecting lines
and new altimeters were installed. The test equipment was then reconnected
to the drain ports in the nose gew wheel well after the
caps were removed and a small thin piece of Teflon tape was wrapped
around the threads prior to torqueing the test fitting. By use of this
procedure the captain's and first officer's NORM&, ALTERNATE, and
AUXILIARY static pressure systems were tested. All systems were within
allowable tolerances.
Both altimeters removed from the aircraft were bench tested in
accordance with the Kollsman Instrument Corporation Service Manual.
The accuracy of the altimeters was within the manufacturer's specifica-
tions. Neither altimeter was marked with low altitude warning markings.
All nine NORMAL, mEFNATE, and AUXILIARY static pressure syste-
drain points were checked for the presence of moisture. None was noted.
A heat test of all NOW, AIXEKNATE, and AUXILIARY static ports on the
left and right sid,es of the fuselage was conducted. All ports were hot
to the touch. Static port heater current draw indicated 9 amperes on
the cockpit ammeter, which is pormal for this system. A heat check was
performed on the captain's and first afficer's auxiliary and alternate
Qitot tubes. All were hot to the touch and indicated normal current draw
tin the cockpit smmeter. A heat check was also performed on the RAT 9
probe and was found to be hot to the touch.
Because of the leakage at the static pressure system drain fitting
caps located in the nose gear wheel well, the Douglas Aircraft Company
was asked to determine what effect this would have on the altimeter
A crosshatching pattern or similar marking to indicate altitudes
from 0 to 1,000 feet.
R B air ~ temperature.

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indications in the cockpit. In response to this inquiry, Douglas
representatives stated: "A detailed flow analysis was therefore made
of the E-9 static system, assuming the leakage associated with a
missing drain fitting cap in order to determine the magnitude of the
error in indicated altitude. The results indicate that . . . at
typical approach conditions with the landing gear retracted and having
the cap entirely missing from the static system drain fitting . . .
the barometric altimeter connected to that static system will indicate
an altitude that is approximately 70 feet higher than normal. The
remaining barometric altimeter, if connected to an integral statia
system, will indicate normally. It is noted that if the subject cap
is simply slightly loo'se, rather than entirely missing, the error
11
will be significantly less. . . .
Flight Data Recorder Tests
As previously noted in Section 1.ll Flight Recorders, the FDR read-
2 out, based on the current calibration of the recorder, dated May 23, 1969,
\ disclosed that the altitude and airspeed parameter recordings were
.( indicating on the high side. As an example, measurement of the zero
a3rspeed position was 1.769 inches from zero reference on the recording
compared with the current calibration level of 1.755 inches, thms refleeting
a difference of 164 knots. This difference was seen to decrease
as the airspeed increased. Table I, following, presents measured values
of altitude on the ground at McAllen and Houston using the M ~ J 23, 1969,
calibration. Recorded pressure altitude is based on the standard barometric
pressure of 29.9 inches of mercury (I@) which is the base setting
of the recorder altitude sensor. Corrected m.s.1. altitude is based on
the actual barometric pressure of 29.86 inches of mercury, the actual
altimeter setting at both stations.
Houston
Intercontinental
0.239 in. 725 ft. 675 ft. 98 ft. 1577 ft.
Because of the marked disparity noted in the altitude and airspeed
parameters in relation to the M ~ J 23, 1969, calibration, the subject
flight recorder' and the foil medium containing the flight record in
question were forwarded to the manufacturer, Fairchild Industrial
Products, for examination and determination of the recorder calibration
as it then stood. This examination was conducted on January 29, 1970,
at the Fairchild facilities in Los Angeles, California, and a new calibration
was obtained which corroborated the condition noted above. The

ecorder condition was not altered in any form during this exmination,
The altitude and airspeed data obtained during the original readout were
recomputed using the recorder calibration received from Fairchild.
Subsequent to the Fairchild examination, arrangements were made
with Texas International Airlines to install the recorder in an aircraft
on a regularly scheduled flight with the Investigator-in-Charge of this
accident riding in the cockpit to monitor and record altitudes and airspeeds
during the flight. The test was conducted on Texas International
Airlines Flight 915, February 17, 1970, between Love Field, hllas, Texas,
and Houston Intercontinental Airport, Houston, Texas, with one en route
stop at Jefferson County Airport, Beaumont/Port Arthur, Texas. The aircraft
was a Douglas Model E-9-30, N8961. A previously mused spool of
foil recording medium was installed in the recorder. The foil medium
was removed at termination of the flight and was forwarded, together with
the flight log prepared by the Investigator-in-Charge, to the National
Transportation Safety Board for examination and readout of the test fligh*
data.
Readout of the recorder test flight record was perfomed separately
on the two flight segments. The readout time periods were 38:30 minutes
and 24:OO minutes respectively for Love Field - Jefferson County Airport
and Jefferson County Airport - Houston Intercontinental Airport. Results
of the readout reflected that the recorder retained the identical disparities
noted in the original readout of the accident flight record.
The zero airspeed position was measured as 1.769 inches from zero reference
and the recorded altitudes at each airport were determined to be
high based on the current calibration. Table 11, following, presents
measured values of altitudes on the ground at the three airports noted
above. The following actual barometric pressure6 were used to determine
the corrected m.s.l. altitudes: (1) 30.00 in. Hg - Love Field, (2) 30.13
in. Hg - Jefferson County Airport, (3) 30.U in. Hg - Houston Intercontinental
Airport.
AImm
Love Field
Jefferson Co.
Rouston
Interconti-
nental
TAEGE I1
CORR3CTED
KECORIIED MEAN SEA PUBLISRED
EilEAsuRFD Pmsw LEVEL AImm
READINGS ALTITUDE ALTITUDE ELEVATION D-CE
0.255 in. 975 ft. 1050 ft. 485 ft. f565 ft.
0,220 in. 425 ft. 625 ft. 16 ft. +609 ft.

-12-
The results of the Fairchild examination of the recorder, on
Janucry 29, 1970, reflect that a permanent shift had occurred in the
altitude and airspeed styli reference positions at some previous time.
The entire record was examined from the accident flight on Side 2 of
the foil back to the firs-trecorded traces on Side 1, where the foil
was first installed. This condition was seen to prevail throughout..
As noted above, exmination of the recorder test flight record reflected
that the condition was unchanged.
A data graph was prepared from the readout of the accident flight
record based on the calibration of the recorder as determined by the
Fairchild examination. The altitude data are based on an actual barometric
pressure of 29.86 inches Kg to convert pressure altitude to
m.s.1. altitude. A time span of 25 minutes (between 3O:OO minutes and
55:OO minutes after liftoff at Miller International Airport, McAllen,
Texas) was omitted from the data graph since it reflects an essentially
steady cruise altitude and airspeed en route to Houston Intercontinental
I
Airport.
k A data graph was also prepared from the readout of the recorder
test flight record based on the calibration of the recorder as determined
by the Fairchild exanation. The altitude data for the first segment
was based on an actual barometric pressure of 30.00 inches Hg for the
takeoff and climb to 18,?00 feet out of Love Field (lk3J.a~) and 30.13
inches Hg for the descent from 18,000 feet to landing at Jefferson Co.
Airport (Beaumont/Port Arthur) to convert pressure altitude to m.s.1.
altitude. AltiCudes above 18,000 feet are pressure altitude uncorrected
(29.9 inches Hg). Altitude data for the second setpent (Jefferson Co.
Airport - Houston Intercontinental Airport) are based on an actual barometric
pressure of 3O.U inches Hg to convert.pressure altitude to m.s.1.
altitude.
The parameters of altitude, airspeed and magnetic heading are uncorrected
for instrument, system or position error and, therefore, are
indicated values.
The initial investigation of this accident eliminated the aircraft
structure, parerplants, and' systems (other than the altimeter/pitot/static
systems) as factors which could be related to the cause of the accident.
The captain's verbal statement on the daq of the accident tpt at
the time the 'khud" was experienced "both altimeters read .m~.fe~et '
inrmediately made the aircraft's alLtimeter/pitot/static systems suspect
and the investigation centered around the examination of these systems.
The captain subsequenw stated that "at this point" his altimeter was
reading "725 to 750 feet" and the copilot's altimeter was reading
"a little below 700, saq appr&imatew 675." Regardless of which of the
two statements is accepted, the magnitude of the error involved is about

-13-
600-to-700 feet as the aircraft was actually about 60 feet m.s.1. when 1
it struck the tree and parer poles. The ground elevation is about 35 L,
feet m.s.1. and the aircraft struck the tree and poles about 25 feet , /
above ground level. ,
.a Tests of the aircraft's e.ltimeter/pitot/static systems revealed
two possible sources of out-of-tolerance leakage: First, the "B" nut
4-
employed to fasten the captain's static pressure line to the starboard
static port in the forward cargo compartment was found not properly
torqued. The nut was properly torqued by tightening 3/h of a turn which
indicates that the leakage, if any, was not substantial. This fitting
is in a pressurized area and, as there was no indicated malfunction of
the pressurization system prior to the accident, any leakage in flight
wuld most probably have occurred as a result of positive pressure in
the cargo ccanpartment entering the captain's static pressure system.
As the aircraft was not flown above 2,000 feet frm MdiUen to Earlingen,
the cargo comparhnent was probably not pressurized and no leakage would
have occurred at the fitting. v t . W been presisuri@,
and if leakage had affected the captain's altimeter indication,
it ~d .~'. ve CUKS-S . . - g e e rdng. The captain stated
ti%t his altimeter read higher thanthe first officer's. Consideration
was given to the possibility that a negative pressure existed in the
cargo compartment. Under this condition, leakage at the ltBtl nut would
have caused a higher-than-normal reading in the captain's altimeter.
This could have accounted for the.discrepancy in the altimeter indications
as stated by the captain which was on the order of 5040-75 feet. The
first officer's altimeter would not have been affected by this improperly
torqued fitting. The first officer was flying the aircraft and should
have been controlling altitude by reference to his altimeter. Also,
the rate of leakage at the static system drain fitting caps (described
next as the second possible source of leabage) was the sane before
and after the "B1' nut was properly torqued. Therefore, the Board
detdnes that this discrepancy did not adversely affect the altltude
indications in the cockpit.
T
The second possible source of out-of-tolerance leakage was at the
statfc pressure system drain fitting caps located in the nose gear wheel
well, in an unpressurized area. Tests conducted by the Douglas Aircraft
Ccpapaqy showed that, under aircraft configuration and flight conditions
sMlar to that of TXI 96 during approach at Earlingen, with a cap
"entirely missing fYom the static system drain fitting . . the baro-
metric altimeter connected to that static system will indicate an
altitude that is approximately 70 feet higher than nod. The remaining
barometric altimeter, connected to an integral static system, wil
indicate normdly. It is noted that if the subject cap is simply
Slightly loose, rather than entirely missing, the error will be signifi-
It
cantly less . . . .
-
A complete check of the aircrapt's altjmeter/pitot/static systems
revealed no other discrepancies.

-14-
A readout of the FDR record disclosed that the altitude and airspeed
parameters were substantidly out of tolerance on the high side
in relation to the most recent calibration data available, dated
Ma~r 23, 1969. Consequently, the subject recorder was forwarded to the
manufacturer, Fairchild Industrial Products, for examination. Their
findings confirmed that the altitude and airspeed recording styli
reference positions were permanently shifted to much higher values
than the standard tolerances. Fairchild determinated the calibration
of the FDR in an "as is" condition. Subsequently the subject FDR was
tested on another aircraft of the sane type involved in the accident.
The FDR readout of the record made during this test flight confirmed
that the FDR was in the same condition as noted originally. The test
flight readout data were computed using both the May 23, 1969, calibration
and the Fairchild calibration data for comparison. Altitude and
airspeed dues derived from the Fairchild data matched closely with
those listed in the flight log prepared by the Investigator-in-Charge
while those clerived from the May 23, 1969, calibration substantiexceeded
the logged dues.
The original FDR readout of the accident flight was recomputed
and plotted using Fairchild's recrllibration data as the more accurate
data. Examination of the accident flight altitude profile shows a
known altitude error of about 181 feet low; i.e., the altitude shown
at takeoff from MFE is -75 feet, the field elevation at "E is ilO6
feet m.s.1. The reason for this error was not determined. A data
graph was prepared with the altitude profile raised 181 feet to correct
for this error (see Appendix C). The following rn.s.1. altitude values
are shown: takeoff at MFE, 106 feet; en route cruise to Rarlingen,
about 1,931 feet (clearance was for 2,000 feet); cross the VOR, l,53
feet (the crew stated that they crossed the VOR at the published
crossing altitude of 1,600 feet); low point during approach at Harlingen,
56 feet (aircraft struck tree and poles about 60 feet m.s.1.); en route
cruise to Houston, about ll,130 feet (clearance was,for ll,OOO feet);
landing at Houston, 181 feet (airport elevation is 98 feet rn.s.1.)-
These indicated altitude values are reasonable and are all within 130
feet of known values or assigned altitudes throughout the flight.
The static pressure source for the FDR in KL30%! is the alternate
static pressure system with static ports which are separate from and
several feet forwssd of the other static ports which are fuselage
mounted on the lower sides of the aircraft. The FDR pitot pressure
source is the rudder limiter "Q-head" which is mounted in the lower
half of the aircraft's vertical stabilizer leading edge. Thus, the
FDR is isolated from the pitot and static pressure systems normdly
providing input to the pnkticdly-operaied cockpit flight instriments.
Therefore, being isolated and andogous to an "independent judeng firm,"
if the FDR indicates that the aircraft is at a certain altitude which is
known to be assigned, such as 2,000 feet between McAllen and Hmlingen,
1,600 feet over the RRL VOR, and ll,OOO feet between Harlingen and
Houston, it is reasoned that the cockpit sltimeters must also be reading

-15- x
at or near that altitude during these relatively stabilized flight conditions.
The test flight of the FDR bears this out. The crew of Flight
926, by reference to their altimeters, apparently had no difficulty in
maintaining the assigned cruise altitudes of 2,000 feet between McAllen
and Harlingen, 1,600 feet over the RRL VOR, and XL,OOO feet between
Harlingen and Houston, within acceptable tolerances. No pbsical evidence
was found to explain w& the captain's and first officer's altimeters
would be reading 600 to 700 feet higher than the actual and corrected
FDR recorded altitude of 56 feet m.s.1. at the time the aircraft struck
the tree and parer poles.
While there was no.xecorded. conversation. &?C the ~.c_rarf.Flight
96 ,requesting or receiving an altimeter setting prior..to .the _=&dent,
the captain did indicate,in a statement dated January 13, 1970, that
I 'We-. ~ ..-'.-,- set .our altimeters,.-..'".'"."~^bu~ he didi,not:Zdiccifii3wt
infCiiion was utilized or w@t settings were used. If the altimeters
were set, they were probably set-€0-field' ~-eiz%€f& while on the ground
at Mcllllen. When the flight, on which Nl308T was used, was terminated
on the day preceding the accident the altimeter setting was 30.01. At
the time of the accident, the altimeter setting at RRL was 29.91, the
equivalent of about 100 feet of altitude. Therefore, if the crew had
not set their altimeters prior to departure at "E their altimeters
would have been reading about 100 feet high. This would cause the aircraft
to actually be 100 feet lower than the indicated altitude. The
recorded cruise altitude between McAlleh and Harlingen was 1,gP feet,
which was 69 feet lower than the assigned altitude of 2,000 feet. The
first officer who was flying the aircraft did not state that he set his
altimeter prior to the accident but the captain stated that he did set
his. This could account for the aircraft's being flown at a lower altitude
than recorded and for the discrepancy stated by the captain relative to
the readings of the two altimeters. The captain's and first officer's
altimeters operate independently of ea& other, each with its own system
and the maximum error involved with either altimeter indication was
100 feet. Subsequent to the accident the altimeters, with identical
altimeter settings set in thewindow of each, indicated within 5 feet
of the same altitude. ~
An analysis of all of the'facts indicates that the aircraft's
altimeters were reading within 130 feet of the actual, assigned, or
recorded altitude for the entire flight from McAllen to Houston, Texas.
The Board finds that the evidence does not substantiatw that both of
the altimeters were in error and indicating 600 to 700 feet higher than
actual altitude during the short period of time in which the accident
occurred. (Seven hundred and fifty feet m.s'.l. is about the dtitude
the aircraft should have been if .they were 100 feet above minimums as
stated by the crew.)
The crew of Flight 926 made no statement relative to their
activities during the night preceding the accident. The Harlingen
Station Manager, a friend of the captain's, stated that he dropped the
,

. -~
-16-
i, captain and first officer off at their motel in McAllen about midnight,
'i after having dimer in Mexico,, The captain and first officer were ob-
,' served in civilian cldthes eating breakfast at a restaurant near their
! motel approximately between 0415 and 0500. The crew's whereaboutm or
activities for the period between midnight and &O was not determined.
The evidence clearly shows that the flightcrew rest was inadequate.
1
4
\
The captain and first officer arrived at the airport ab& 0630
for gn 0631 scheduled departure and, therefore, only minimal flight
preparation was accomplished. The captain picked up the flight papers
in TXI Operations. These contained the 0500 ERL weather, sharing clear
skies/visibility 5 miles with fog, but did not contain the 0600 HRL
weather, sharing clear skies/visibility 1 mile with fog. The 0600 HRL
weather report was not disseminated to McAllen due to the heavy workload
of compw personnel at the TXI Haxlingen station in connection with the
anticipated arrival and departure of two flights. Had the captain been
less rushed, he would most likely have noted this discrepancy and could
have obtained the latest HRL weather by radio or telephone prior to
departure. The weather at M&en at 0630, which the crew was well amre
of, was sw partially obscured and visibility 1/4 mile in fog. It should
have been readily apparent to them that the weather at Wlingen (about
35 miles away) would most likely be worse than the 0500 report: clear
skies and 5 miles visibility in fog.
Flight 96 tooic off from McAllen at 0651, about 21 minutes after
the flightcrew arrived at the airport. About 4 minutes after departure
the captain contacted BRO APC and received a VOR approach clearance to
Rarlingen. En route to Herlingen the captain attempted to contact the
compw radio at Harlingen but was unsuccessfbl. The evidence shows that
initi- he was unsuccessAil because of the workload at Harlingen, but
rirsimstely he did contact the station.
The first officer's only knowledge of the weather was the 0500
ERL weather, which shared 5 miles visibility, and his actual observations
of the weather during the flight. He probably made a mental note of the
7OO-foot fog top during the departure climbout from McAllen. The sQ was
clear above. The top of the fog at Hexlingen was 450 feet m.s.1. Examination
of the FDR readout shows the following: after Flight 926 passed the
HRL TOR it started a descent from 1,600 feet and turned to the right frcnn
a heading of 075" to intercept the 108" radial. During the next 35
seconds, the turn continued to a heading of about 142' and the descent
continued to an altitude of about 600 feet, where the flaps were extended
to 15". (At this point, because the circling minimums were 600 feet and
l* miles visibility, the first officer should have leveled the aircraft
and continued at 600 feet until the runwqy was in sight.) A few seconds
after the flaps were extended, the first officer realized that he had
passed through the 108" radial and stexted a turn to the left. Abut 5
seconds after cmencing this turn, the aircraft entered the fog. The
turn continued to the left to a heading of about 97" and this heading
was held for about 40 seconds until the accident occurred. During this
40-second period, the altitude varied fram 200 feet to 300 feet to 250
feet to 56 feet where the accident occurred.

-17- ._
The Board believes that the descent below minimums was made by
the first officer because he believed the visibility to be about 5
miles and he was expecting to see the and airport lights about
lminute after passing the VOR. For the first 20 seconds after entering
the fog, the first' officer was faced with reintercepting the 108"
radial and his attention was probably devoted primarily to thls
activity and looking out of the cockpit for the runway and airport light&,
while the aircraft continued to descend to 200 feet. After the aircraft
was established on the 108" radial, the first officer most likely
dwoted most of his attention to heading control and looking out of the
cockpit for airport lights, as the variance of altitude during this
period indicates inadequate monitoring and control.
After the aircraft passed the VOR, the captain's attention was
initially devoted primarily to attempting to contact Harlingen on the
cmp- radio, extending the flaps for the first officer and looking
out of the cockpit for the runway and airport lights as he too believed
6 the visibility to be 5 miles. This belief is substantiated by a company
emplayee at Harlingen who stated, "The MWen agent, Mr. Jobnny Vasquez,
advised me that flight 926 was trying to contact us on the company radio,
I then went to the operations room to moniter (sic) the radio. I called
for flight 926, and they answered immediately, flight 926 asked what
our iate weather was 80 I gave them the 0655 observation, which I had
just taken. I advised 926 that Emlingen haa -X skies and about 112
mile visibility with fog. I gave the wind direction as 30 degrees at
six knots. Flight 926 then replied that the last weather they had was
11
clear skies and five mile visibility and that he was on final. . . ,
This occurred at the approximate point where the captain stated, .'!Gib,
hold it there," .and shortly before qO0 when~the--~~r-~-st.,;uk the tree
and power poles. Contriifto' the-caltain's~.vi-~~t-~s statement,
"Gib, hold it there," was ae.-as-&~re;gglt.of.his obs-Wi+iition-.of a discrepancy
in the altimeter readings, the Board believes that the statement
was madq as a result of his receiptlLof the new weathx.&fo.p$ion. The
accident occurred a fPeW seconds iater GiXTemm,, crew could adequate&
e'valmte the situation and take corrective adion.
2.2 Conclusions
(a) Findings
I
1. There was no failure or miifmction of the aircraft or
its powerplant s .
2. The two possible sources of out-of-tolerance leakage
found in the aircraft static pressure systems would have had no appreci-
able effect ofithe cockpit altitude indicators. With the exception of
these two possible discrepancies, the remainder of the altimeter/pitot/
static systems functioned normally.
3. There was no failure or miifmction of any of the other
aircraft systems.

-18-
-4. The crew was properly certificated for the flight and
examination of crew data showed they were qualified.
8. The 0500 Harlingen weather was reported as clear with
'
1
5 miles visibility. This was the latest weather information innnediatdy
available to the crew prior to departure from McAllen and they made no
attempt to procure the latest Harlingen weather prior to the 0651
departure.
I 9. The 0600 Harlingen weather report, reported 1 mile
4visibility. Tbis report was not disseminated because of the heavy workload
at the company's Harlingen station.
10. After departure fram McAllen the crew was not able to
contact the Harlingen TXI company radio because, due to the heavy workload
at Harlingen, the company radio was unattended.
ll. The first officer, who was flying the aircraft, was
not emme of the actual weather conditions at Harlingen. The latest
Harlingen weather he was awe of was that contained in the 0500 report.
E. The captain was not aware of the actual weather conditions
at Harlingen until he was informed of them by a Harlingen TXI agent who
radioed the information a few seconds prior to the accident.
13. The FDR showed that the aircraFt was flown atbin 130
feet of the known, assigned, or published altitudes for the entire
flight from takeoff at M&en to landing at Houston.
(b) Probable Cause

3. RECOMMEMIATIONS AND CORRFICTTVE MEASUKES
During the course of this investigation the Board noted that
some altimeters installed on Texas International Airlines, Inc.,
aircraft were "crosshatched" adjacent, to the zero to 1,000 feet
atitude range, while others were not.
On November 20, 1970, the Safety Board sent a letter to the
Administrator of the FAA reconmending that, in order to preclude
hlisreading or dsinterpretation of altimeters at low altitudes, he
condder requiring standardization of altimeter low altitude warning
markings within an air carrier or air taxi operator if feasible, or in
aqy case within their particular type aircraft. (See Appendix D. )
On January 16, 190, the Federal Aviation Administration
mended the operations specifications of Texas International Airlines,
Inc., by increasing their altitude and visibility landing minimums by
'i100 feet and I/& &e.
On January 19, 1970, management personnel at Texas International
Airlines, Inc., implemented procedures to improve and increase pilot
proficiency.
BY THE NATIONAL TRANSPORTATION SAFETY BOARD:
.. ~ .
December 2, 1970.
/s/ JOHN H. REED
Chairman
/si/ OSCAR M. LAUREL
Member
/s/ FRANCIS H. McADAMS
Member
/s/ LOUIS M. THAYER
Member
/s/ ISABEL A. BURGESS
Member
x

1. Investigation
The Board received notification of the accident at approximately
0905 c.s.t. on January ll, 1970, from the Federal Aviation Administra-'
tion. An investigator from the NTSB Field Office in Fort Worth, Texas,
was inmediately dispatched to Houston, Texas, where the aircraft had
landed. Formal worldng groups were not convened for the investigation
of this accident; however, various representatives of the
Federal Aviation Administration; Texas International Airlines, Inc.;
the Air Line Pilots Association; McDonnell Douglas Corporation; and
Fairchild Camera and Instment Corporation participated in the
investigation and provided technicall assistance. The on-scene investigation,
which was accomplished at both Houston and Harlingen, Texas,
was completed January 14, 1970.
2. Hearing
A public hearing was not held.
3. Preliminary Report
A preliminary aircraft accident report summarizing the facts,
circwnstances, and conditions of the accident as they were lmown at
the time, was published on February 24, 1970.

I- HAKCIILLINI
I
8. I 0
PULL UP to 1600 feet, turn LEFT to HRL VOR.
APPENDIX B
JUl I869
03-1) HARLINGEN, TEXAS
Apf. Elev 35' HARLINGEN INDUSTRIAL
35'